Conventionally, plasma processing apparatuses utilizing plasma have been used in manufacturing processes of semiconductor devices and liquid crystal display devices to perform film deposition, etching or the like on substrates thereof. In recent years, with a considerable increase in size of the substrates of the semiconductor devices and the liquid crystal display devices, plasma processing apparatuses capable of processing large-area substrates have been developed. Particularly, with advancement in studies of the use of a rectangular substrate having a size of no smaller than one square meter for the liquid crystal display device, a plasma processing apparatus capable of processing such a large-size substrate has been developed. One of the most critical issues for the plasma processing apparatus of this kind is to improve uniformity and controllability of the process, or, to improve uniformity and controllability of the plasma.
An inductively-coupled plasma source and a plasma source utilizing microwaves provide a greater degree of freedom in process control, compared to a capacitively-coupled plasma source primarily used conventionally, since the plasma source and the biased state of the substrate can be controlled independently from each other. Thus, from the standpoints of uniformity and controllability of the process described above, the inductively-coupled plasma source and the plasma source utilizing the microwaves have come to be widely used, replacing the conventionally used capacitively-coupled plasma source.
In the plasma sources as described above, however, a dielectric member such as a dielectric window is used for supplying energy for plasma generation into a processing chamber where plasma processing is to be performed. This requires appropriate setting of shape and size of the dielectric member in order to efficiently supply the energy into the processing chamber. Particularly in the case of electromagnetic waves of short wavelengths such as microwaves, whose wavelength is sufficiently small compared to the size of the processing chamber, the size of the dielectric member as well as the mode of the microwaves transmitted through the dielectric member would largely affect efficiency in propagation of the microwaves. The propagation efficiency of the microwaves affects generation efficiency of the plasma. In other words, it affects the range of process conditions enabling plasma generation.
A technique of defining a size of the dielectric member to optimize the propagation efficiency of the microwaves is disclosed, e.g., in Japanese Patent Laying-Open No. 8-315998. The publication describes that transmission efficiency of the microwaves in a dielectric microwave transmitting member is optimized by setting the plate thickness of the microwave transmitting member to an integer multiple of approximately half the wavelength of the microwaves within the microwave transmitting member.
A technique taking account of a mode of microwaves to generate uniform plasma is disclosed, e.g., in Japanese Patent Laying-Open No. 5-275196. In this publication, it is described that a mode filter is used to restrict the number of propagation modes of microwaves having a plurality of modes including a higher order mode, to thereby obtain microwaves of substantially a single mode, which is then used to generate uniform plasma.
The conventional techniques described above, however, pose the following problems.
In the technique disclosed in Japanese Patent Laying-Open No. 8-315998, the plate thickness of the microwave transmitting member is set to an integer multiple of approximately half the wavelength of the microwaves, as described above. In the publication, quartz is shown as a material of the microwave transmitting member, and a wavelength of microwaves within a free space, taking account of a relative dielectric constant of the quartz, is used as the wavelength of the microwaves within the microwave transmitting member of quartz. The microwave transmitting member, however, has a finite size, and thus, the wavelength of the microwaves propagating through the microwave transmitting member becomes longer than the wavelength of the microwaves propagating through the free space. Further, the wavelength of the microwaves propagating through the microwave transmitting member changes according to the mode and shape of the microwaves. It is considered that it would be difficult to effectively optimize the propagation efficiency of the microwaves with the technique disclosed in Japanese Patent Laying-Open No. 8-315998 that gives no consideration to the above-described points.
In Japanese Patent Laying-Open No. 5-275196, the number of propagation modes of microwaves having a plurality of modes including a higher order mode is restricted so as to generate plasma using microwaves of substantially a single mode, as described above. However, the publication describes that the microwaves are made to have substantially a single mode within a waveguide through which the microwaves propagate. It gives no specific consideration to the mode of the microwaves within a member made of a dielectric through which the microwaves propagate. It is thus considered that there would be cases where it is difficult to effectively improve the propagation efficiency of the microwaves within the dielectric member.
The present invention has been made to solve the above-described problems by providing a plasma processing apparatus and a processing apparatus capable of widening a process condition range enabling plasma generation by increasing propagation efficiency of microwaves.